The manufacture of color cosmetics, such as foundations, blushes, eyeshadows, lipsticks, as well as other colored materials, such as inks, necessarily involves a step of incorporating pigments into the formulation. When the final product has a liquid, particularly aqueous, base, the incorporation of the pigment is problematic, as the most commonly used pigments, such as titanium or iron oxides, are insoluble particles which do not easily blend into the liquid base. These particles can be physically dispersed in water. Once incorporated, however, particles can tend to reagglomerate due to the natural incompatibility of the pigments with water in the formulation; particles can also be adversely affected by the liquid environment, resulting in a loss of color stability. This can give rise to a product which is non-uniform, and unacceptable both to the manufacturer and to the average consumer.
In an effort to enhance the dispersibility of pigment particles and to hinder tendencies for reagglomeration, the industry has often turned to coating of pigment particles. Pigment coatings are chosen for their ability to render the coated particles more compatible with the environment in which they are to be used. Such coating materials are well-known, and have been described for example in U.S. Pat. Nos. 4,349,389; 5,013,543; 3,546,008; 3,734,874; 3,779,993; and 4,233,196. The coatings described in the latter four references, which are polyesters and polyesteramides, are particularly useful for preparing water-dispersible pigments. However, the recommended method for preparation and dispersion of the coated pigments is a wet process, using relatively small quantities of coating. Although to some extent effective, this methodology can result in incomplete coating of the pigment, which can ultimately permit reaggregation of the pigments. The wet preparation process also results, even after drying, in a pigment which does not store well for long periods of time and may be subject to bacterial contamination. The present invention now provides a dry treated pigment which is stable even after prolonged storage time, and which disperses easily, and without reagglomeration, in an aqueous base.